In many industries and applications there has been a shift away from printing documents on bond paper, including transaction documents (e.g., receipts, tickets, gift certificates, sweepstakes and the like), toward printing documents on direct thermal paper (e.g., thermal media).
Security features for determining the authenticity of printed transaction documents have been used on transaction documents employing single-sided direct thermal media. However, security features in the transaction documents that would mitigate fraud more completely have remained illusive. For example, the lottery industry has employed secure ticketing applications, required security controls, preprinted security features, and designed strict security methods to validate and authenticate winning lottery tickets.
Direct thermal printers have been used to image the thermal media. Often, information is printed or imaged only on one side of the document. Dual-sided direct thermal printing of documents, such as transaction documents, is described in U.S. Pat. Nos. 6,784,906 and 6,759,366. In dual-sided direct thermal printing, the printer is configured to allow concurrent printing on both sides of a thermal media moving along a feed path through the thermal printer. In such a printer, a direct thermal print head is disposed on each side of the thermal media along the feed path. In operation, each thermal print head faces an opposing platen across the thermal media from the respective print head. During printing, the opposing print heads selectively apply heat to the opposing sides of the thermal media, which comprises a substrate with a thermally sensitive coating on each of the opposing surfaces of the substrate. The coating changes color when heat is applied, such that printing is provided on the coated substrate.
As the authenticity of documents is of importance in many industries and applications, it would be advantageous to provide improved dual-sided thermal security features to mitigate fraud.